LSM YSZ Research Articles

The effect of glass sealing stabilization on LSM–YSZ cathode poisoning and oxygen reduction reaction processes in solid oxide fuel cell

AbstractThe perovskite structure and electrochemical activity of (La0.80Sr0.20)0.95MnO3−x–(Y2O3)0.08(ZrO2)0.92 (LSM–YSZ) composite cathode can be significantly affected by volatile boron species originated from sealing glass–ceramics. Herein, we investigate the impact of doping the varying Er2O3 content (ranging from 0 to 4%) into an aluminoborosilicate glass to mitigate boron volatilization, its interaction with the LSM–YSZ cathode and consequent effects on its electrochemical performance. The results reveal that the volatility of boron species can be significantly suppressed by introducing Er oxide into the glass network by enhancing the conversion of [BO3] to [BO4] units, thereby increasing the binding energy of boron and strengthening of the glass structure. Moreover, the electrocatalytic performance for the O2 reduction reaction on the LSM–YSZ/8YSZ/LSM–YSZ symmetric cells is studied under open‐circuit conditions in the presence and absence of glass sealants. The analyses utilizing electrochemical impedance spectroscopy (EIS) and distribution of the relaxation times (DRT) analysis indicate that the electrocatalytic performance of LSM–YSZ cathodes can be enhanced in the presence of glass with 4% Er2O3 (GE4). This enhancement in the electrocatalytic activity of the LSM–YSZ electrode for the oxygen reduction reaction (ORR) is attributed to formation of the thin layer on the electrode surface, leading to a notable reduction in the polarization resistance (Rp) from 0.81 Ω cm2 in the glass absence to 0.45 Ω cm2 in the presence of GE4. However, DRT analysis demonstrates that the prolonged exposure of the cathode to GE4 causes a deterioration in cell performance primarily due to the blocking the cathode active sites, which impedes dominant cathode processes of oxygen dissociative adsorption/desorption and charge transfer and consequently reducing kinetics of the ORR.

(Digital Only Presentation) Effects of Ink Solvent on the Screen-Printing Fabrication and Morphology of LSM-YSZ Thin Films Deposited on YSZ Substrate for Solid Oxide Electrochemical Cells

Screen-printing is a cheap and easy thin film deposition technique utilized in energy devices fabrication, specifically, in solid oxide electrochemical cells (SOCs). This technique offers simple set-up, film quality control and mass production. In this study, LSM-YSZ, a promising component material for SOCs application was deposited on YSZ electrolyte via screen-printing. Specifically, the study aimed to investigate the effect of the solvent used in screen-printing on the quality of the deposited film. LSM-YSZ precursor powders synthesized via glycine-nitrate combustion process (GNP) were screen-printed on YSZ substrate using different solvents, ethanol and alpha-terpineol. The structure, morphology, and conductivity values of the GNP LSM-YSZ thin films using two solvents were compared. Results showed that both solvents produced a uniform distribution of rhombohedral LSM and cubic YSZ thin films with porous morphologies but alpha-terpineol solvent exhibited more agglomerated particles. Despite having this morphology, alpha-terpineol is still preferred than ethanol due to its reproducibility and scalability as it is less volatile than the other one. Moreover, there was no significant difference between the measured total conductivities of the half-cells using two solvents with the values of 4.63e-3 S/cm and 2.07e-3 S/cm at 700°C, and activation energies of 0.374 eV and 0.483 eV from 500°C - 700°C, for ethanol and alpha-terpineol, respectively.

(Digital Only Presentation) Effects of Ink Solvent on the Screen-Printing Fabrication and Morphology of LSM-YSZ Thin Films Deposited on YSZ Substrate for Solid Oxide Electrochemical Cells

Screen-printing is a cheap and easy thin film deposition technique utilized in energy devices fabrication, specifically, in solid oxide electrochemical cells (SOCs). In this study, LSM-YSZ, a promising component material for SOCs application was deposited on YSZ electrolyte via screen-printing. Specifically, the study aimed to investigate the effect of the solvent used in screen-printing and the effect of varying ink formulation on the quality of the deposited film. LSM-YSZ precursor powders synthesized via glycine-nitrate combustion process (GNP) were screen-printed on YSZ substrate using ethanol and alpha-terpineol solvents. The structure and morphology of LSM-YSZ thin films using two solvents were compared. Results showed that both solvents produced a rhombohedral LSM and cubic YSZ thin films and the use of a-terpineol solvent with higher solid content produced a desired uniform and porous morphology with homogenous pore distribution as revealed by XRD and SEM morphological results.

Interaction of O2 with LSM–YSZ Composite Materials and Oxygen Spillover Effect

The interaction between gas-phase oxygen and LSM–YSZ (LSM is La0.6Sr0.4MnO3±δ; YSZ is ZrO2·Y2O3 electrolyte) composite catalytic materials was studied by the in situ method based on isotope equilib...

Topology optimization of the microstructure of solid oxide fuel cell cathodes

Thermal mismatch significantly influences the stress state and lifetime of solid oxide fuel cells (SOFCs). The microstructure of the LSM–YSZ cathode is optimized by using the asymptotic homogenization method and three-phase material topology optimization to improve thermal mismatch. Two orthogonal microstructures are obtained by taking minimum thermal mismatch as the object with some constraints. The microstructures constitute a cathode in the form of periodic fiber bundles. Results show that the coefficients of the thermal expansion of the microstructures are almost equal to those of the electrolyte layer at different temperatures, thus eliminating thermal mismatch. The microstructures have higher effective ion conductivity than typical cathodes. The optimization results are helpful for the design of future electrodes.

Oxygen-Electrode-Supported Solid Oxide Cells with High Fuel and Steam Utilization

Oxygen-electrode-supported solid oxide cell (SOC) designs are potentially advantageous for electrolysis and reversible energy-storage applications. In a reversible SOC application, the oxygen produced during electrolysis can be stored and then used during fuel cell operation. In this case, the presence of pure oxygen at the oxygen electrode mitigates the significant gas diffusion limitations encountered with thick oxygen electrode supports when using air. Furthermore, supporting the cell mechanically with the oxygen electrode allows the fuel electrode to be significantly thinner, which alleviates gas diffusion limitations that make it difficult to achieve high steam utilization during electrolysis operation, and high fuel utilization in fuel cell operation. Nevertheless, development of oxygen-electrode-supported cells has been hampered by processing limitations, particularly the difficulty in co-firing oxygen electrode materials with higher melting temperature electrolyte materials to achieve a fully densified electrolyte while retaining satisfactory electrode porosity, surface area, and triple-phase boundary density (TPB), and avoiding undesirable interfacial reactions or interdiffusion. Electrolyte sintering aids can help reach desirable co-firing temperatures. In previous work, sintering aids were used for single-step co-firing temperature of fuel-electrode supported SOCs and resulted in cells with desirable microstructure, free of significant interdiffusion, and relatively good performance, but also with low TPB density and therefore high polarization resistance in the oxygen electrode compared to cells fabricated by a two-step firing process. In this work, we demonstrate successful fabrication of oxygen-electrode-supported SOCs consisting of LSM current collector, LSM-YSZ oxygen-electrode, YSZ electrolyte, and NiO-YSZ fuel electrode, using a reduced-temperature single-step firing process. Microstructural and chemical characteristics of the cell components are studied using scanning electron microscopy and energy dispersive spectroscopy. The electrochemical characteristics are studied using current-voltage measurements and impedance spectroscopy, with both air and pure oxygen at the oxygen electrode and with different H2/H2O contents at the fuel electrode. These cells achieve much better fuel or steam utilization than anode-supported cells due to the relatively thin fuel electrode, and the presence of pure oxygen in the oxygen-electrode support mitigates mass transport limitations. Cells operating in fuel cell mode tested with hydrogen and air produce a maximum power density (Pmax) of 325 mW/cm2 at 800 °C, with a limiting current density of 0.9 A/cm2. Pmax increases to 575 mW/cm2 when using pure oxygen as oxidant, due to the improved gas diffusion and a larger exchange current density in the cathode. LSM-YSZ electrodes of some cells are infiltrated with (Sm0.5Sr0.5)CoO3 (SSC), and enhancement of the electrode in this manner is critical for obtaining high cell power density. Incorporation of SSC nanoparticles increases Pmax to 580 mW/cm2 for a cell operating in fuel cell mode in hydrogen and air, with much smaller initial resistance compare to the non-infiltrated cell. Limiting current is similar to the non-infiltrated cells, suggesting large gas diffusion limitation due to the thick oxygen electrode. Changing the oxidant from air to pure oxygen results in significant improvement in cell performance, with Pmax of 1400 mW/cm2 and no evidence of limiting current up to 6 A/cm2, the highest current measured. Life tests were carried out on SSC-infiltrated cells operating at a direct current of 1 A/cm2 and temperature of 800°C in both fuel and electrolysis modes. Significant degradation was observed, primarily due to coarsening of the infiltrated SSC. Recent results using a different infiltrant, Sr(Ti,Fe)O3, which show better stability, will be presented. Finally, initial results on another method for reducing concentration polarization, via the use of patterned electrode supports made using an extrusion-based 3D-printing process, will be presented.

Degradation kinetics of LSM–YSZ cathode materials for SOFC

Solid oxide fuel cells are perspective electrochemical devices for hydrogen energy applications and require long time performance. The paper studies the influence of the processes of particles coarsening and cation interdiffusion on the degradation kinetics of the LSM–YSZ cathode material catalytic activity as related to the interaction processes with oxygen from the gas phase. The exchange kinetics with the gas phase oxygen was studied by the oxygen isotope exchange method with the gas phase equilibration at the temperature of 850 °С and Po2 = 10−2 atm. The samples were exposed for 1000 h. The coefficient of gas phase and surface oxygen exchange was found to decrease at the exposure. The paper discusses the physical reasons, which lead to the oxygen surface exchange coefficient decrease in LSM–YSZ electrodes and degradation of the polarization conductivity measured by electrochemical impedance spectroscopy.

Particle-Scaled Visualization of Active Sites in LSM/ScSZ Composite Cathode of SOFC through Oxygen Isotope Labeling

Introduction Composite electrodes such as LSM/ScSZ or LSM/YSZ are widely used as a cathode material of SOFC. In these electrodes, both triple phase boundary (TPB) consisting of LSM, ScSZ, and gas phases and double phase boundary (DPB) between LSM and gas phases are considered to work as an active site for oxygen reduction.1 Length of TPB, surface area of DPB, and spatial distribution of those have a great impact on electrochemical performance of cathode. Such kind of geometrical information can be investigated by focused-ion beam scanning electron microscope (FIB-SEM) while almost no information about active reaction site distribution or oxide ion path in composite cathode has been obtained so far. Atomic labeling using isotope oxygen is a powerful tool to investigate oxide ion flow in SOFC materials, and has been mainly applied to pattern electrode experiments to investigate reaction paths at anode or cathode.2 Here, we first conduct particle-scaled visualization of active site in composite LSM/ScSZ cathode by oxygen isotope labeling. Methods, Results, and Discussions A YSZ electrolyte-supported cell with Ni/YSZ anode and LSM/ScSZ cathode was fabricated for the experiment. Wight ratio of LSM and ScSZ is 1:1. In order to quench a reaction in a SOFC cell within a short time during operation at high temperature, a power generation equipment with a nozzle for a helium impinging jet, which is covered by a water cooling jacket, was prepared. At first, the cell was operated in 50% H2-50% Ar for the anode side and in pure 18O2 for the cathode side at 1073 K for 3 minutes. After that, the cell was cooled to below 423 K within 1.5 sec. by the helium impinging jet. The 18O distribution in cross section of the cathode was obtained by secondary ion mass spectroscopy (SIMS) with a spatial resolution of 50 nm (NanoSIMS 50L, CAMECA). In this work, 18O concentration mappings of an interface between LSM/ScSZ cathode and YSZ electrolyte under OCV and 0.11 A/cm2 were obtained. The mappings of LSM (red) and ScSZ or YSZ (green) and of 18O concentration denoted by the ratio of 18O-/(16O- + 18O-) under 0.11 A/cm2 are shown in Figures 1(a) and 1(b), respectively. At cathode part, 18O diffuses to only ScSZ phase uniformly under OCV condition, which is driven by the isotopic oxygen concentration difference. On the other hand, relatively high 18O intensity (0.2-0.25) is observed at LSM particles near the cathode/electrolyte interface under 0.11 A/cm2 as shown in Fig. 1(b). This means that 18O diffuses into LSM particles only near the cathode/electrolyte interface. Isotopic exchange experiment of LSM-patterned cathode on YSZ was conducted by Horita et al.2 Their work disclosed that diffusion of oxide ion into LSM bulk under the higher cathodic polarization is promoted than that under the lower. This is because under the higher cathodic polarization, charge transfer currents increase and active sites are expanded from TPB to DPB. From Fig. 1(b), more charge transfer currents are generated at LSM particles in the region within about 3µm from the cathode/electrolyte interface than at other regions. This result gives the first direct evidence that reaction sites near the cathode/electrolyte interface are more electrochemically active than those at other regions, which has been predicted by electrochemical measurements and numerical simulations.3 Acknowledgements SIMS analysis was conducted at Advanced Characterization Nanotechnology Platform of the University of Tokyo, supported by "Nanotechnology Platform" of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Chemical Stability of La 1-X Sr x Mn0.8Ni0.2O3-δ x={0.1 to 0.5} Cathode Compositions with 8YSZ at High Temperature

Ni-added LSM compositions (La 1-x Sr x Mn0.8Ni0.2O3 with x={0.1 to 0.5}) and YSZ mixtures (50/50 wt%) were used for evaluating their chemical stability at high temperature (1300oC). Ni-added LSM raw powders were fabricated by using a glycine route. X-ray diffraction was used to quantify and identify crystallographic phases. DC four-probe measurement was used for electrical characterization. Results show that Ni-addition at the B-site of LSM structure is effective for suppressing the secondary phase formation, particularly La2Zr2O7, when strontium content is between 0.1≤x≤0.2. Electrical conductivity was about 100 S cm-1 within the chemically stable strontium content range. Therefore, it is expected that suppression of La2Zr2O7 formation at high temperature could improve SOFC performance, especially during long time operation, thus supporting the co-sintering of a whole SOFC ceramic stack at high temperature.

A porous yttria-stabilized zirconia layer to eliminate the delamination of air electrode in solid oxide electrolysis cells

Abstract Delamination of La 0.8 Sr 0.2 MnO 3-δ (LSM) in solid oxide electrolysis cells (SOECs) is usually associated with the high oxygen partial pressure build-up at the LSM-YSZ (yttria-stabilized zirconia) interface. Here we sandwich a porous YSZ layer between the LSM electrode and YSZ electrolyte to release this oxygen pressure. Symmetric cells with and without the porous YSZ layers are prepared and tested in air at 800 °C under the current densities of 0.5 and 1 A cm −2 for 100 h. Voltage change is continuously monitored, and impedance spectrum studies have been carried out before and after testing. No delamination has been observed for the samples with the porous YSZ layer even after 100 h. The improved performance for these samples is due to the shift of oxygen evolution reaction from the dense YSZ-LSM interface to a porous YSZ-LSM interface. This shift also helps the oxygen to be easily released instead of going into the pores or grain boundaries of the electrolyte. On the other hand, for the sample without the porous YSZ layer, the LSM is totally delaminated from the electrolyte just after 70 h.

Electrochemical behaviors of infiltrated (La, Sr)MnO3 and Y2O3–ZrO2 nanocomposite layer

(La0.8Sr0.2)0.9MnO3−δ-Y0.15Zr0.85O1.93 (LSM–YSZ) nanocomposite layer is infiltrated into three different scaffolds of ion-conductive YSZ, ionic and electronic conductive LSM–YSZ composite and insulating Al2O3 and used as cathode for anode supported cells. The cell performance and impedance spectra analysis reveal that the LSM–YSZ nanocomposite layer shows considerable high ORR activity using its own electronic and ionic conducting network, however, the electrochemical performance seems to be constrained by its limited ionic and electronic conductivity. The construction of ionic conducting path using YSZ scaffold is more effective for raising electrochemical performance than the construction of both electronic and ionic conducting paths using LSM–YSZ composite scaffold.

Degradation of solid oxide cells during co-electrolysis of steam and carbon dioxide at high current densities

Abstract In this work, the durability of Ni–YSZ based solid oxide cells was investigated during co-electrolysis of steam and carbon dioxide (45% H 2 O + 45% CO 2 + 10% H 2 ) at current density of −1.5 or −2.0 A cm −2 . The cell consists of ∼300 μm Ni–YSZ support, ∼10 μm Ni–YSZ electrode, ∼10 μm YSZ electrolyte and ∼15 μm LSM–YSZ oxygen electrode. The gas conversion was 45% at −1.5 A cm −2 and 60% at −2.0 A cm −2 , and the operating durations were up to 700 h. The detailed electrochemical analysis revealed significant increase of the ohmic resistance, oxide ion transport resistance in the Ni–YSZ composite electrodes and the electrochemical reaction resistance at the Ni–YSZ triple-phase boundaries. The performance degradation is mainly ascribed to the microstructural change in the Ni–YSZ electrode close to the YSZ electrolyte, including the percolation loss of Ni, the contact loss between Ni and YSZ electrolyte and the decomposition of YSZ close to Ni–YSZ|YSZ interface. The electrochemical performance and the microstructure of the oxygen electrode were found to be relatively stable.

Co-synthesized (La0.8Sr0.2)0.9MnO3[sbnd]Y0.15Zr0.85O2 composite for solid oxide fuel cell cathode

(La0.8Sr0.2)0.9MnO3Y0.15Zr0.85O2 (LSM–YSZ) composite co-synthesized by citrate-nitrate combustion method are investigated for solid oxide fuel cell cathode. The co-synthesized LSM–YSZ composite powders are characterized by XRD, HR-SEM, TEM, HR-TEM and EDX analysis. The phase separation of the precursor into LSM perovskite and YSZ fluorite occurs at temperatures above 900 °C, about 200 °C higher than the formation temperature of pure LSM or pure YSZ. In the nano-sheets of LSM–YSZ composite, nano-particles of LSM and YSZ are well distributed and intimately contacted with each other. The nanostructures remain in the co-synthesized LSM–YSZ cathode. The co-synthesized LSM–YSZ cathode improves oxygen reduction reaction (ORR) activity, especially at reduced operation temperature. The cell with co-synthesized LSM–YSZ cathode delivers current density 150% times of the cell with traditional LSM–YSZ cathode at 600 °C. Electrochemical impedance spectra (EIS) analysis shows that oxygen reduction reaction is accelerated due to high three phase boundary (TPB) density. The co-synthesized LSM–YSZ cathode shows good stability under cell operation at 800 °C.

Effect of GDC addition method on the properties of LSM–YSZ composite cathode support for solid oxide fuel cells

Equal amounts of Gd0.1Ce0.9O2−δ (GDC) were added to La0.65Sr0.3MnO3−δ/(Y2O3)0.08(ZrO2)0.92 (LSM/YSZ) powder either by physical mixing or by sol–gel process, to produce a porous cathode support for solid oxide fuel cells (SOFCs). The effect of the GDC mixing method was analyzed in view of sinterability, thermal expansion coefficient, microstructure, porosity, and electrical conductivity of the LSM/YSZ composite. GDC infiltrated LSM/YSZ (G-LY) composite showed a highly porous microstructure when compared with mechanically mixed LSM/YSZ (LY) and LSM/YSZ/GDC (LYG) composites. The cathode support composites were used to fabricate the button SOFCs by slurry coating of YSZ electrolyte and a nickel/YSZ anode functional layer, followed by co-firing at 1250°C. The G-LY composite cathode-supported SOFC showed maximum power densities of 215, 316, and 396mWcm−2 at 750, 800, and 850°C, respectively, using dry hydrogen as fuel. Results showed that the GDC deposition by sol–gel process on LSM/YSZ powder before sintering is a promising technique for producing porous cathode support for the SOFCs.

Degradation Kinetics of LSM–YSZ Composite Materials

The paper studies the influence of the processes of particle coarsening and cation interdiffusion on the degradation kinetics of catalytic activity of LSM–YSZ composite materials in relation to the process of interaction with oxygen from the gas phase. The oxygen exchange kinetics with the gas phase has been studied by means of isotope exchange method with gas phase equilibration at T = 850 °C and Po2 = 10–2 atm. Samples were tested during 1000 hours. It is shown that the oxygen exchange coefficient with the sample surface decreases with the increasing of exposure time. The paper discusses the physical causes leading to a decrease of the oxygen exchange coefficient.

Feasibility of alternative electrode materials for high temperature CO2 reduction on solid oxide electrolysis cell

The electrochemical performance of Ni–gadolinia-doped ceria (GDC) cathode was studied for CO2 reduction on solid oxide electrolysis cell (SOEC) at 1000 °C and compared with that of Ni–yttria stabilized zirconia (Ni–YSZ) cathode. Ni–GDC cathode demonstrated higher performance for CO2 reduction. Furthermore, lanthanum strontium cobalt ferrite (LSCF) anode exhibited lower overpotential than lanthanum strontium manganite–yttria stabilized zirconia (LSM–YSZ) anode. Ni–GDC cathode and LSCF anode were found to be stable under a constant current density of −0.90 A cm−2 at 900 °C. Moreover, no substantial performance degradation was observed for the cell having Ni–GDC cathode and LSCF anode even after 9 h of electrolysis operation under a constant current density of −1.2 A cm−2 at 1000 °C.

Pinning-down polarization losses and electrode kinetics in cermet-supported LSM solid oxide cells in reversible operation

The impedance behavior of the archetypal Ni–YSZ/YSZ/LSM–YSZ solid oxide cells was investigated in reversible operation at different humidity conditions up to 90%. The major electrode polarizations of the full cell at 850°C are identified with the electrochemical polarization of the LSM–YSZ electrode modeled by three-parameter transmission line model and the gas concentration impedance of the Ni–YSZ electrode modeled by an ideal Gerischer element. The gas concentration polarization increases with the dehumidification by the electrolysis, which is thus reduced by the increased ambient humidity. Capacitance effects vary oppositely. According to the non-faradaic chemical reaction controlled mechanism for the electrochemical reaction suggested by Mizusaki, diffusion–reaction parameter for LSM electrode was estimated from the transmission line model analysis. Surface diffusivity is shown to enhance strongly with oxygen activity induced by electrolysis, which can be partly ascribed to the decreased surface adsorption capacitance as well as increased mobility. Surface reaction rate increase essentially reflects the decreased adsorption capacitance. The kinetics becomes more limited by the surface adsorption reactions but overall diffusion-limited, which is represented by the Gerischer-like response. Less pronounced performance deterioration in SOFC operation may be ascribed to the mixed conduction contribution.

Comparison of performance and degradation of large-scale solid oxide electrolysis cells in stack with different composite air electrodes

Three hydrogen electrode-supported, large-scale solid oxide electrolysis cells (SOECs) with different composite air electrodes, namely LSM–YSZ, LSC–GDC, and LSCF–GDC (LSM, LSC, and LSCF cells, respectively), were compared for performance and degradation in the same three cell stack with an H2O/H2 ratio of 90/10. The initial SOEC performance increased in the following order: LSM, LSCF, and LSC. The three cells were operated at a constant current density of 0.50 A cm−2 for 640 h during hydrogen production at 750 °C. After the operation, the 10 cm × 10 cm large-scale single cell was divided equally into four subparts from the two diagonal parts with the steam or air inlet area and steam or air outlet area for post-mortem analysis. Delamination mainly occurred in the steam and air inlet areas of the LSM and LSC cells, with more severe delamination in the steam inlet area than that in the air inlet area. Agglomeration of Ni in the Ni–YSZ hydrogen electrode was observed in the LSM and LSCF cells, whereas honeycomb Ni was observed in the steam and air inlet areas of the LSC cell.

Degradation of (La(0.8)Sr(0.2))(0.98)MnO(3-δ)-Zr(0.84)Y(0.16)O(2-γ) composite electrodes during reversing current operation.

Reversing-current operation of solid oxide cell (La(0.8)Sr(0.2))(0.98)MnO(3-δ)-Zr(0.84)Y(0.16)O(2-γ) (LSM-YSZ) oxygen electrodes is described. Degradation was characterized by impedance spectroscopy in symmetric cells tested at 800 °C in air with a symmetric current cycle with a period of 12 hours. No change in cell resistance could be detected, in 1000 h tests with a sensitivity of ∼1% per kh, at a current density of 0.5 A cm(-2) corresponding to an overpotential of 0.18 V. At a current density to 0.6 A cm(-2) (0.33 V overpotential) measurable resistance degradation at a rate of 3% per kh was observed, while higher current/overpotential values led to faster degradation. Degradation was observed mainly in the ohmic resistance for current densities of 0.6, 0.8 and 0.9 A cm(-2), with little change in the polarization resistance. Polarization degradation, mainly observed at higher current density, was present as an increase in an impedance response at ∼30 kHz, apparently associated with the resistance of YSZ grain boundaries within the electrode. Microstructural and chemical analysis showed significant changes in electrode structure after the current cycling, including an increase in LSM particle size and a reduction in the amount of YSZ and LSM at the electrode/electrolyte interface - the latter presumably a precursor to delamination.

Particle Coarsening Influence on Oxygen Reduction in LSM–YSZ Composite Materials

AbstractThe microstructure influence on the oxygen reduction process for the LSM–YSZ composite materials has been studied in this paper. To localize the effect of particle coarsening influence, the oxygen isotope exchange measurements with the gas phase analysis have been performed for LSM–YSZ | YSZ | LSM–YSZ symmetric cells during 300 and 1000 hours at T = 850 °C and Po2 = 10−2 atm. In order to find quantitative relations the changes in the oxygen surface exchange and the diffusion coefficients and its microstructure parameters such as porosity and triple phase boundary (TPB) length have been compared. The rate determining stage of the LSM–YSZ degradation has been suggested to be the LSM‐phase surface diffusion and the LSM surface diffusion coefficient have been estimated.